The purpose of this study is to determine and compare the efficacy and toxicity of T-SMZ/AZT, P-S/AZT and AP/AZT in preventing recurrent pneumocystis carinii pneumonia (PCP) and extending survival in AIDS patients who have recovered from their initial episode of PCP; to determine the pharmacokinetics of T-SMZ and P-S in patients receiving AZT and the effects of their administration on the pharmacokinetics of AZT.